Asymmetric Structure-Induced d-Orbital Splitting Boosts Highly Active and Stable Li-CO₂ Batteries

Lithium-carbon dioxide (Li-CO₂) batteries provide an extremely feasible strategy for sustainable development and carbon neutrality. However, due to the sluggish kinetics and complex interfacial reactions, Li-CO₂ batteries are limited by low output voltage and poor cycling stability. Developing efficient and durable catalysts remains an urgent challenge. Transition metal oxides have gained significant attention owing to their availability and stability for electrocatalytic reactions, but their catalytic activity remains unsatisfactory toward Li-CO₂ batteries. Herein, this work proposes an asymmetric Fe/Cu-incorporated Co₃O₄ tactic system to tune charge distribution for motivating efficient electrocatalysis and decipher the mechanism of asymmetric structure modulation on the promotion of catalytic activity and stability. It is unraveled that d-orbital spin splitting induces the modification of nondegenerate state, which enhances catalyst durability, while simultaneously increasing electron occupancy in d_{xz / yz} orbitals. This higher electron occupancy facilitates the hybridization with the p orbitals of reactants and intermediates via π bonding, thereby strengthening the adsorption activity. In consequence, the Li-CO₂ battery with Cu-Co₃O₄ cathode demonstrates a low overpotential of 0.73 V and high Coulombic efficiency of 96%, outperforming batteries with Co₃O₄ and Fe-Co₃O₄. This work offers a unique insight for electronic structure regulation strategy and displays a high-performance catalyst for Li-CO₂ batteries.